A mid turbine frame (MTF), sometimes referred to as an inter turbine frame, is located generally between turbine stages of a gas turbine engine to support one or more bearings and to transfer bearing loads through to the outer engine case, and also to form an inter-turbine duct (ITD) for directing a hot gas flow to the downstream rotor. It is conventional to have a conduit carrying a lubricant fluid to pass through one of the radial hollow airfoils disposed in the ITD. The airfoils are exposed to the hot gas flow in the ITD and therefore an insulation system is demanded for the conduit because the hot temperature may cause lubricant degradation or even lubricant ignition if lubricant leakage occurs. Conventional insulation systems for oil lines in MTF has relatively complicated structures which demand spaces and weights.
Accordingly, there is a need to provide an improved oil tube insulation.